SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES • NUMBER 7 The Distributional Ecology and Zoogeographical Relationships of Stomatopod Crustacea from Pacific Costa Rica Marjorie L. Reaka and Raymond B. Manning OCT -7 !9P0 SMITHSONIAN INSTITUTION PRESS City of Washington 1980 The Distributional Ecology and Zoogeographical Relationships of Stomatopod Crustacea from Pacific Costa Rica Marjorie L. Reaka and Raymond B. Manning Introduction not the West Atlantic; and species in several other East Pacific stomatopod genera (Eurysquilla, Co- The biota of the East Pacific region is relatively ronida, Lysiosquilla, and Pseudosquillopsis) show clos- poorly known, despite its considerable Zoogeo- est affinities to species in the East Atlantic (Man- graphie significance. The East Pacific has been ning, 1977). On the other hand, some species of separated from the West Atlantic region since the mollusks occur in the Atlantic and Indo-West late Miocene (Durham and Allison, 1960; Wood- Pacific, but not the East Pacific (see Woodring, ring, 1966), and, although high levels of ende- 1966; Emerson, 1978). Species of four stomatopod mism are found there, many East Pacific species genera (Bathysquilla, Odontodactylus, Alima, Pseudo- show affinities to taxa in the West Atlantic squilld) are present in the West Atlantic and Indo- (Woodring, 1966; Briggs, 1974; Manning, 1977; West Pacific, but not in the East Pacific (Man- Emerson, 1978). However, some East Pacific spe- ning, 1969a; Manning and Struhsaker, 1976). An cies are more closely related to taxa in the East Atlantic than to those in the West Atlantic. For alpheid shrimp, Alpheusparacrinitus Miers, 1881, is example, a xanthid crab, Nanocassiope melanodactyla known from the Indo-West Pacific, Clipperton (A. Milne-Edwards, 1867), is known from the Island in the East Pacific, and the East Atlantic, East Pacific and East Atlantic but not from the but does not occur on the East Pacific mainland West Atlantic (Chace, 1966). The closest relatives or in the West Atlantic (Chace, 1962). of five species of East Pacific xanthid crabs (some The fauna of the offshore islands in the East of them restricted to the Galapagos) occur in the Pacific (Isla Guadalupe, Islas Tres Marias, Islas East Atlantic (Garth, 1968). One stomatopod de Revillagigedo, Clipperton, Clarion, Cocos, and crustacean, Squilla aculeata, is represented by sub- the Galapagos) is particularly interesting, inas- species in the East Pacific and East Atlantic but much as Indo-West Pacific species often occur in relatively high proportions there but not on the Majorie L. Reaka, Department of Zoology, University of Maryland, mainland. Of 24 species of nonbrachyuran deca- College Park, MD 20740. Raymond B. Manning, Department of Invertebrate Zoology, National Museum of Natural History, Smith- pod crustaceans found on Clipperton Island sonian Institution, Washington, D.C. 20560. (Chace, 1962), 14 (58%) are known from other 1 SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES offshore islands and the Indo-West Pacific. Of the West Atlantic than to those in mainland East these 14 species, six do not extend beyond the Pacific areas (Briggs, 1974). offshore islands, four reach the East Pacific main- In summary, most East Pacific species are re- land, and four occur also in the Atlantic. The lated to other taxa in their region or in the West remaining 10 species are restricted to the East Atlantic. Some species, however, particularly Pacific, and three of them are endemic to the those from outlying areas of the East Pacific, offshore islands. Of 34 species of brachyuran most closely resemble species from the Atlantic decapods found on Clipperton, 15 (44%) occur (sometimes the eastern West Atlantic or the East also in the Indo-West Pacific; eight of these spe- Atlantic), providing a distributional hiatus in cies occur only as far east as the offshore islands mainland East Pacific and/or Caribbean regions. (Clipperton), and seven reach the mainland. The Furthermore, a number of species occur in Atlan- tic and Indo-West Pacific regions, but not in the remaining 19 species occur only in the East Pa- East Pacific. Although a number of Indo-West cific (Garth, 1965, 1974). In the Galapagos, Garth Pacific migrants cross the East Central Pacific (1946) found 120 species of brachyurans; five expanse to the offshore islands, few traverse the (4%) occur also in the Indo-West Pacific, 18 are relatively minor remaining distances to the main- endemic to the Galapagos, and most of the re- land. These faunal relationships obviously raise maining species occur only in the East Pacific; questions about patterns of habitat use and evo- either the same or the closest relatives of four lutionary processes along East Pacific shores. species occur in the West Atlantic. Of nearly 3400 Herein we present an annotated list of the mollusks in the East Pacific, only 48 (ca. 1%) shallow-water stomatopod Crustacea collected have Indo-West Pacific affinities. However, ex- during the R/V Searcher Expedition to the Pacific cept for the rare occurrences of 10 of them on the coast of Costa Rica in 1972, of which one of us mainland, 79% of the species with Indo-West (M.L.R.) was a member. Stomatopods are active Pacific affinities are restricted to the offshore predators that occupy burrows in mud, sand, islands (Emerson, 1978). The incidence of Indo- coral, and under rocks, and are important com- West Pacific elements in the molluskan fauna of ponents of tropical communities both in numbers the Islas de Revillagigedo (3%), Cocos (7%), and of individuals and in potential impact upon prey the Galapagos (5%) is lower than that for Clip- species (Abele, 1972, 1974; personal observation). perton (60%) (Briggs, 1974). Vermeij (1978) has A raptorial appendage is used to hammer and characterized some of the biological attributes of spear prey, to fight other stomatopods, and for mollusks that do and do not cross this offshore defense against predators. Severe, potentially le- barrier. Also, relatively high proportions of Indo- thal fights erupt among individuals of the same West Pacific species are found on the offshore and other species of mantis shrimps; this intense islands for corals (56% Cocos, 22% Galapagos) aggression appears to be related to defense of the and fishes (23% Islas Revillagigedo, 26% Clipper- burrow (Caldwell and Dingle, 1975). In spite of ton and Cocos, 12% Galapagos) (Briggs, 1974). behavior characteristic of intense competition, we Indo-West Pacific fishes occupy localized coral know relatively little about the frequency of spe- habitats in the Golfo de Chiriquí, Panama, and cies exclusion or co-occurrence in these pugna- similar outposts near Nayarit and Cabo San Lu- cious predators. Furthermore, we have only mea- cas, Mexico, as well. However, even in these ger knowledge about the range of habitats occu- localities, Indo-West Pacific fishes appear to be pied by particular taxa. Such information is crit- less abundant than endemic species (Rosenblatt, ical for interpretation of behavioral studies (re- McCosker, and Rubinoff, 1972). Like the brach- ported elsewhere; Reaka and Myers, manuscript yurans, a number of endemic fishes from the in preparation). Also, patterns of local distribu- Galapagos are more closely related to species in tion and habitat use shed light on ecological and NUMBER 7 TABLE 1.•Collections of stomatopods from the Pacific coast of Costa Rica (station numbers refer to the R/V Searcher data log, Cruise 72-3, Costa Rica, Chief Scientist W. A. Bussing, Universidad de Costa Rica) Date Habitat and Collecting Station Locality Species (¡972) notes method 447 9 Mar Bahia Herradura Gonodactylus bahia- 20 m, tip of outer reef, ichthy- 9°38'45"N, 84°40'- hondensis mud, shell, rocks, little if ocide, 55"W G. costaricensis any coral, sand pockets, SCUBA surge 450 10 Mar same as Sta 447 G. albicinctus 17 m, side of outer reef, same Meiosquilla oculinova habitat same as station squillid postlarva 447 451 10 Mar Bahia Herradura squillid larva 37 m, across mouth of bay, 15' otter 9°38'50"N, 84°40'- squillid postlarva mud trawl 50"W 455 10 Mar Bahia Herradura Squilla panamensis 55 m, offshore from Bahia 9°39'30"N, 84°42'- Herradura, mud 05"W 462 11 Mar near Punta Quepos M. swetti 21 m, large porous rubble ichthy- 9°22'43"N, 84°09'- Heterosquilla mccullochae ocide, 41"W SCUBA 464 12 Mar Isla Salera (near Punta M. oculinova 17 m, rocks same Quepos) G. stanschi 9°22'12"N, 84°09'- G. bahiahondensis 15"W G. sp. juveniles 471 14 Mar Isla del Caño M. oculinova 9 m, sand, coral, rubble same 8°43'15"N, 83°53'- G bahiahondensis 07"W G stanschi G. zacae G costaricensis G. albicinctus Nannosquilla californiensis H. mccullochae 472 14 Mar Isla del Caño G. zacae 15 m, pinnacle with rocks same (same as Sta 471) G. bahiahondensis and coral rubble, sand gonodactylid larva around base, lysiosquil- M. oculinova lids from sand, others M. swetti from rubble H. mccullochae Acanthosquilla bimimensis Nannosquilla canica - - Isla del Caño G. zacae intertidal pool, in and un- collected G. festae der coral rubble and by hand G. bahiahondensis basalt boulders G. stanschi G. costaricensis Gonodactylus juveniles M. oculinova 482 17 Mar Isla del Caño G zacae 37 m, reef pinnacle 1.5 mi ichthy- 8°43'10"N, 83°54'- from island, rocks and ocide, 30"W coral rubble SCUBA 483 17 Mar near Isla del Caño A. biminiensis 20 m, lee of island, sandy same bottom SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES TABLE 1.•continued Date Habitat and Collecting Station Locality Species (1972) notes method 484 17 Mar near Isla del Caño squillid postlarva 62 m, mud, poor yield of 30' otter 8°44'20"N, 83°53'- other animals trawl 20"W 485 17 Mar near Isla del Caño Pseudosquillopsis 73 m, mud same 8°46'35"N, 83°54'- marmorata 00"W Parasquilla similis Squilla aculeata Cloridopsis dubia near Isla del Caño Lysiosquilla desaussurei surface hand net at night light 487 18 Mar Isla del Caño G.